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HomeMy WebLinkAboutCOM 0246.015 2012-2014 CCUTY CLERK R. Flint Hughes, Ph.D. Research Ecologist 2013 AUG 20 PH q8 Institute of Pacific Islands Forestry USDA-Forest Service 60 Nowelo Street Hilo, HI 96720 Phone: 808 933-8121 Fax: 808 933-8120 Cell: 808 430-0662 Dear Sir or Madame: Aloha. Please note that I am submitting testimony in strong support of County Council Bill. This Bill and the actions to come from it are sorely needed. I include the following documentation of the management issues surrounding this fast-growing and hazardous tree. Invasive alien species have caused untold damage to the ecology and economies of areas they have invaded (Elton 1958). Where invasive species introduce new biological processes or disturbance regimes into ecosystems, they have the potential to profoundly alter both community characteristics and ecosystem functions, often to the extreme detriment of the native flora and fauna being invaded (Vitousek et al. 1987, D'Antonio and Vitousek 1992). The invasive alien tree, Falcataria moluccana (Miq.) Barneby and Grimes (synonyms: Paraserianthes falcataria (L.) I.C. Nielsen, Albizia falcataria (L.) Fosberg, Albizia falcata auct) is a very large, fast-growing, nitrogen-fixing tree in the legume family (Fabaceae) (Wagner et al. 1999). It is a daunting invasive species, in that it is considered to be the fastest growing tree species in the world, capable of growing ca. 2.5 cm in height per day (Footman, 2001, Walters 1971). Further, individuals reach reproductive maturity by the age of four years and subsequently produce copious amounts of viable seed (Parrota 1990) contained within seed pods that are wind-dispersed and can be carried substantial distances (i.e., > 200 m) up- and down-slope during windy conditions. When mature, the canopy of an individual tree is capable of extending over a one-half hectare area, and the broad umbrella-shaped canopies of multiple trees commonly coalesce to cover multiple hectares and even up to square kilometers (Hughes and Denslow 1995). Perhaps the single most important constraint to Falcataria seedling recruitment is light availability; seedlings are very sensitive to shade and germinate in abundance only where the overstory canopy is open enough to allow sufficient light penetration (Soerianegara and Lemmens 1994). Although valued by some, F. moluccana has become invasive in forests and developed landscapes across many Pacific islands. Native to the Moluccas, New Guinea, New Britain, and Solomon Islands (Wagner et al. 1999), F. moluccana was imported to a wide variety of islands across the Pacific, typically for the purpose of providing shade for, and litter-derived nitrogen additions to, crop species. It is currently considered Comm. ' • /c Ref.To: Ref. Date. 2 0 Mil invasive in the Republic of Palau, Pohnpei, Yap, New Caledonia, Fiji, Independent Samoa, American Samoa, the Cook Islands, the Society Islands, and the Hawaii Islands (Space 20??), and it is present though not yet considered invasive in the islands of Guam, Wallis and Futuma, and Tonga (Space 200?get references). Given the widespread presence of F. moluccana across the Pacific Islands, this species poses a serious threat to the highly diverse biological hotspot that these islands collectively constitute (Myers et al. 2000). An archetypical early successional (i.e., pioneer) species, F. moluccana is generally found in mesic to wet forest environments and favors open, high light environments such as disturbed areas; its capacity to readily acquire nitrogen via its symbiotic association with Rhizobium bacteria makes it able to colonize even very young, highly N-limited lava flows such as those found on Hawaii Island (Hughes and Denslow 2005). F. moluccana was first introduced to the Hawaiian Islands from Borneo and Java in 1917 by the explorer botanist — and champion of native Hawaiian species — Joseph F. Rock (Rock 1920). Rock noted the rapid growth rate of F. moluccana, stating that it is capable of reaching a height of over 35 m in 25 years time and that, "trees nine years old had reached a height of over a hundred feet, a rapidity of growth almost unbelievable". Ironically, Rock also commented on the life cycle of F. moluccana, stating that, "the only objection to the tree is its short-lived period, but as it is an abundant seeder, there should always be a good stand of this tree present" (Rock 1920). Regarding the life span of F. moluccana, individuals planted by Rock in 1917 remain living, nearly 100 years later, on the grounds of the Lyon Arboretum on Oahu, Hawaii. Following its introduction, F. moluccana was one of the most commonly planted tree species in the concerted, long-term, and wide-ranging non-native tree establishment efforts conducted by Hawaii Territorial and State foresters during the early to mid- 1900's; approximately 140,000 individuals were planted throughout the Forest Reserve systems across the Hawaiian Islands, and populations have spread extensively from those intentional plantations (Skolmen and Woodcock refs here). ECOLOGICAL IMPACTS Previous research on the impacts of F. moluccana on native forests in Hawaii have demonstrated that whereever it invades this species profoundly transforms these forests by dramatically increasing inputs of nitrogen, facilitating invasion by other weeds while simultaneously suppressing native species. Hughes and Denslow (2005) described the impacts of F. moluccana invasion on some of the last intact remnants of native wet lowland forest ecosystems undergoing primary succession in Hawaii. They found that primary productivity in the form of litterfall was more than 8 times greater in F. moluccana-dominated forest stands compared to stands dominated by native tree species. More importantly, N and P inputs via litterfall were up to 55 and 28 times greater in F. moluccana stands compared to native-dominated forests (Hughes and Denslow 2005), and rates of litter decomposition - as well as rates of N and P release during decomposition - were substantially greater in F. moluccana invaded forests relative to native-dominated forests (Hughes and Uowolo 2006). These nitrogen inputs of up to 240 kg N ha-1 y-1 in F. moluccana stands exceed typical application rates of N fertilizer documented for industrial, high output corn cropping systems of the US Midwest (Jaynes et al. 2001). As a consequence, soil N availability was 120 times greater in F. moluccana forests relative to native-dominated forests on comparably- aged lava flow substrates. Simultaneously, F. moluccana invasion increased soil enzyme activities - particularly acid phosphatase (AP) activities — and converted the fungal-dominated soil communities of native stands to bacteria-dominated soil communities in F. moluccana-invaded stands (Allison et al. 2006). These profound functional changes coincided with dramatic compositional and structural changes as well; F. moluccana facilitated and explosive increase in densities of understory alien plant species — particularly Psidium cattleianum, and native species — particularly the overstory tree, Metrosideros polymorpha — suffered widespread mortality to the point of effective elimination from these areas that they had formerly dominated. Based on these findings, Hughes and Denslow (2005) concluded that the continued existence of native-dominated lowland wet forests in Hawaii largely will be determined by the future distribution of F. moluccana. In American Samoa, where F. moluccana (locally known as tamaligi) was introduced in the very early 1900's and was present across 35% of the main island of Tutuila by 2000, an aggressive campaign has been undertaken by federal, state, and local groups to control and ideally eradicate this invasive species from the island (Hughes et al. 2012). Research addressing both the capacity for F. moluccana to displace native forest communities potential for native forest recovery following its removal, supports both the need for control of this tree as well the perspective that eradication is actually a feasible objective in these ecosystems. Results indicate that F. moluccana displaces native trees; although aboveground biomass of intact native forests did not differ from those invaded by F. moluccana, greater than 60% of the biomass of invaded forest plots was accounted for by F. moluccana, and biomass of native species was significantly greater in intact native forests. Following the removal F. moluccana (i.e., killing of mature individuals), the native Samoan tree species grew rapidly, particularly those which exhibit early successional, or pioneer species traits. The presence of such pioneer-type tree species appeared to be most important reason why F. moluccana removal is likely successful management strategy; once F. moluccana is removed, native tree species grow rapidly, exploiting the legacy of increased available soil N - left from F. moluccana litter inputs - and available sunlight. Recruitment by shade intolerant F. moluccana seedlings was severely constrained to the point of being non-existent, likely a result of the shade cast by reestablishing native trees in management areas (Hughes et al. 2012). Although F. moluccana is a daunting invasive species, it exhibits characteristics that make it vulnerable to successful control: it is easily killed by girdling or herbicides, and its seeds and seedlings do not tolerate shade. These characteristics, combined with the important capacity for rapid growth exhibited by many of Samoa's native trees, actually create conditions and opportunities for successful, long-term control of F. moluccana in lowland forests of American Samoa. SOCIO-ECONOMIC IMPACTS F. moluccana is also a roadside, urban forest and residential pest of major significance. Because individuals rapidly and routinely reach heights of up 40 m and their weak wood breaks easily in storms or with age, catastrophic failure of massive limbs create significant hazards in residential areas and across infrastructure corridors such as roads and power lines, and their management is extremely costly for landowners, utilities, and local governments. For example, on April 16, 2010, a 25 to 30 m tall F. moluccana tree fell across a residential street in the Puna District of Hawaii Island that destroyed power lines and fences and landed in a backyard area where children often play (Hilo Tribune Herald, May 6, 2010). The economic burden posed by removal of large F. moluccana individuals from high-use public areas is profound. The potential economic burden posed by F. moluccana is staggering. In 2009, on the island of Kauai the Hawaii Department of Transportation (HDOT) was compelled to act on two unconfirmed near fatalities involving large branches of F. moluccana dropping onto cars and on an adjacent house located close to the road right-of-way. In response, the HDOT spent one million dollars to remove approximately 1,500 F. moluccana individuals growing along a single mile of roadway. Because F. moluccana has such soft wood and unstable branches, arborists were forced in this case to employ expensive cranes and lifts to remove these trees. As a consequence the larger trees cost in excess of $10,000 per individual to remove safely. Across the state of Hawaii, it has been estimated that over 40% of HDOT damage claims involving falling trees and branches are due to F. moluccana individuals and populations. Even where F. moluccana individuals grow at some distance from roads, they are considered problematic and hazardous because limbs can fall into waterways and accumulate against bridges, potentially causing flooding and physical damage to critical infrastructure. In addition, natural events such hurricanes or storms often cause extreme damage to F. moluccana stands which in turn contribute to road closures, electrical outages, and property damage, thus exacerbating post storm and cyclone cleanup and repair work all across the state of Hawaii. It is currently estimated that there are between 50 to 100 miles of state roads along which F. moluccana populations are maturing, growing in size and reaching high densities (personal communication, Christopher A. Dacus, Landscape Architect and Certified Arborist, Hawaii State Department of Transportation). With no natural predators to constrain them, both the size and areal extent of F. moluccana populations are increasing in both stature and areal extent, with concomitant maintenance costs increasing annually as well. CONTROL MEASURES In American Samoa, successful efforts to control F. moluccana populations within the Tutuila unit of National Park of American Samoa and adjacent lands employed a girdling method whereby field crews of 2-6 people incised the bark of each mature individual at its base using bark spuds and manually peeled the bark up the trunk in large strips. This is done around the entirety of the trunk, resulting in a 1-3 m wide section where the outer bark is removed. Following girdling, individual trees died gradually, but inevitably, between 6 months to a year following treatment. This approach has been successful for three main reasons. First, significant funding was available to implement and execute F. moluccana control across the targeted areas of infestation; as of this writing, NPSA field crews have killed over 6,000 mature trees, thus restoring approximately 1,500 ha of native Samoan forest. Second, overwhelming public support for F. moluccana control effort has been cultivated through outreach and informational meetings with local village leadership, employment of villagers residing adjacent to areas of infestation, and use of media outlets on a consistent basis. Third, F. moluccana exhibits characteristics that make it vulnerable to successful control: it is easily killed by girdling or herbicides and its seeds and seedlings are exceedingly shade intolerant, and many of the common native Samoan tree species recover quickly from disturbance through the shade they cast, preempt subsequent F. moluccana seedling recruitment (Hughes et al. 2012). Herbicides have also proven to be effective in controlling saplings and larger, mature F. moluccana individuals. On the Hawaiian Island of Molokai, the Molokai-Maui Invasive Species Committee spearheaded a multi-agency effort in July, 2008 to eliminate a large stand of F. moluccana who's large and extensive root systems were threatening to damage significant and sensitive cultural sites. Field crews girdled the trees with chainsaws and applied Garton 3A mixed with crop oil. Significant canopy defoliation was noted within weeks of treatment and mortality of treated trees was 98% one year following application, and 100% mortality with no subsequent seedling recruitment 4 years post-treatment. As of this writing, all known populations of F. moluccana on Molokai have been killed, providing a compelling example of island-wide eradication of this highly invasive tree. As in American Samoa, the F. moluccana control project proved highly successful in bringing together disparate community members, interagency staff, and cultural practitioners, and participants are determined to use this project as a model for community involvement and creating a proper emphasis on Hawaiian cultural practices. Encouraging recent advances in the development and use of another herbicide, Milestone® (EPA reg. no. 62719- 519; active ingredient aminopyralid), has provided a highly effective means by which to quickly and efficiently kill mature F. moluccana. Milestone is administered by injection of very low volume, metered doses of the undiluted formulation to kill and control infestations of Falcataria moluccana. This new method - a method demonstrated to be much more effective and hygienic than current conventional methods now being employed — appears to be a "game changer", allowing for efficient, safe, and successful control of F. moluccana populations across broad landscapes of Hawaii (personal communication, James Leary, Invasive Weed Management Specialist, University of Hawaii). Trials indicate that very low dosage treatments resulted in near 100% mortality in less than one month's time. As such herbicide approaches employing Milestone application should prove to be an important component to future F. moluccana control efforts do to its efficacy, and ease of application. BIOCONTROL EFFORTS While girdling and herbicide applications been shown to be effective means to kill and control saplings and mature trees, more challenging is control of the massive seedling recruitment that occurs once mature individuals have been killed. This is particularly true in Hawaii, where fast-growing pioneer-type tree species are not well expressed in the native flora (Wagner et al. 1999). Identifying appropriate bio-control agents is a logical and compelling solution to this challenge. Recent bio-control programs targeting Acacia species have met with considerable success by focusing on agents that attack reproduction to reduce spread of trees from existing stands. At present, several potential bio-control agents appear worth considering for investigation. Two of those agents, pink disease (Corticium salmonicolor) and a particular gall rust (Uromycladium tepperianum) have been identified as damaging pests of F. moluccana growing in plantations of South-East Asia (Su-See 1999). In addition, seed feeders have been successfully employed in South Africa to control a close relative of F. moluccana, the Australian tree Paraserianthes lophantha (Donnelly 1992, Dennill et al. 1999, Schmidt et al. 1999). Seed predators are a promising potential bio-control agent for F. moluccana as ongoing herbicide trials demonstrate the ease in which mature individual can be dispatched; if post-control recruitment could be minimized through seed predation, effective control of F. moluccana populations in Hawaii would be feasible. The benefits of a combined chemical and biological control program for F. moluccana would likely extend to tropical islands throughout the Pacific. Further loss of native forests and biodiversity in the Pacific can be expected from F. moluccana invasion if chemical and biological control work is not initiated. CONCLUSIONS Previous research and recent experience demonstrates that, left unchecked, F. moluccana invasion poses significant threats to both the integrity of native ecosystems and human health and welfare across the Pacific Islands. Successful containment of F. moluccana by self-perpetuating bio-control agents along with chemical control measures also result in savings of many millions of dollars throughout the Pacific by avoiding damage and maintenance costs associated with these trees growing near utilities, roads, homes and workplaces. REFERENCES CITED Allison SD, Nielsen C, Hughes RF. 2006. Elevated enzyme activities in soils under the invasive nitrogen-fixing tree Falcataria moluccana. Soil Biology and Biochemistry 38:1537-1544. D'Antonio, C. M., P. M. Vitousek. 1992. Biological invasions by exotic grasses, the grass fire cycle, and global change. Annual Review of Ecology and Systematics 23: 63-87. Dennill, G.B., D. Donnelly, K. Stewart, and F.A.C. lmpson. 1999. Insect agents used for thebiological control of Australian Acacia species and Paraserianthes lophantha (Fabaceae) in South Africa. African Entomology Memoir No.1: 45-54. Donnelly, D. 1992. The potential host range of three seed-feeding Melanterius spp. (Curculionidae), candidates for the biological control of Australian Acacia spp. And Paraserianthes (Albizia) lophantha in South Africa. Phytophylactica 24: 163- 167. Hughes RF, Denslow JS. 2005. Invasion by an N2-fixing tree, Falcataria moluccana, alters function, composition, and structure of wet lowland forests of Hawai'i. Ecological Applications 15:1615-1628. Hughes RF, Uowolo A. 2006. Impacts of Falcataria moluccana invasion on decomposition in Hawaiian lowland wet forests: The importance of stand-level controls. Ecosystems 9:977-991. Hughes RF, Uowolo AL, Togia TP. 2012. Effective control of Falcataria moluccana in forests of American Samoa: Managing invasive species in concert with ecological processes. Biological Invasions. Doi: 10.1007/s10530-011-0164-y. Jaynes DB, Colvin TS, Karlen DL, Cambardella CA, and Meek DW. 2001. Nitrate loss in subsurface drainage as affected by nitrogen fertilizer rate. Journal of Environmental Quality 30: 1305-1314. Myers, N., R. A. Mittermeier, C. G. Mittermeier, G. A. B. da Fonseca, J. Kent. 2000. Biodiversity hotspots for conservation priorities. Nature 403: 853-858. Su-See L. 1999. Forest health in plantation forests in South-East Asia. Australasian Plant Pathology 28: 283-291. Vitousek, P. M., L. R. Walker, L. D. Whitaker, D. Mueller-Dombois, and P. A. Matson. 1987. Biological invasion by Myrica faya alters ecosystem development in Hawaii. Science 238: 802-804. Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii Press, Honolulu. Walters, G.A., 1971. A species that grew too fast — Albizia falcataria. Journal of Forestry 69: 168.